The complex numbers Z and W are given by Z=3+3i and W=6-i. Giving your answers in the form of x+yi and showing how you clearly obtain them, find: i) 3Z-4W ii) Z*/W

i) 3Z-4WFor this question it is just the matter of substituting the complex numbers of Z and W into the equation. So, 3(4+3i)-4(6-i). Then multiply out the brackets to get 12+9i-24+4i. Finally simply to get -12+13i.This question is worth two marks and you get awarded one mark for the real part and one mark for the imaginary part.ii)Z*/WIn this question we are asked to divide the complex conjugate of Z by W. Z* = 4-3i, so Z*/W = *4-3i)/(6-i).To solve this we must make the denominator real. This is similar to rationalizing surds, the trick here is to multiply by the conjugate, so we get ((4-3i)x(6+i))/((6-i)(6+i))No we carefully multiply out to get (24+4i-18i-3i^2)/(36-i^2). The important part of multiplying by the complex conjugate is so that the complex part of the denominator cancels. Now we simply to get (27-14i)/37 remembering that i^2=-1Finally the last step is to write the answer in the form of x+yi to ensure we get full marks which is simply (27/37)-(14/37)iThis question was worth 4 marks. You get one mark for writing down the conjugate of Z correctly, you got a method mark for multiplying by the conjugate of W and then two accuracy marks for finding the real and imaginary parts.

JB
Answered by James B. Maths tutor

6959 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

Find the area enclosed between the curves y = f(x) and y = g(x)


Write down two reasons for using statistical models


Find dy/dx when y=(3x-1)^10


ABCD is a rectangle with sides of lengths x centimetres and (x − 2) centimetres.If the area of ABCD is less than 15 cm^2 , determine the range of possible values of x.


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2026 by IXL Learning